Tropomyosin and allergic reactions

September 04, 2017

Tropomyosin and allergic reactions

When it comes to allergy to edible insects, we're speaking about allergy to tropomyosin.

Tropomyosins are a family of molecules present in the muscles of all living beings: vertebrates, molluscs, insects etc. Essentially, each species has its own kind of tropomyosin. Many have tryed the one present in the dust mite after having come in contact with them, or after a house-dust inhalation!

The tropomyosin is a molecule consisting of a series of aminoacids that are repeated and shaped in a double-helix filament recalling that of the DNA. The aminoacids sequences are different from species to species. Some sequences, however, are so similar that cross-allergy phenomena are not uncommon.The cross-allergy is that phenomenon whereby those who have developed allergic sensitization against dust mites tropomyosin for instance, will be also sensitive to that present in crustaceans and shellfish.

Allergy to tropomyosin

But what is the action mechanism of an allergic reaction?

The allergic reaction is triggered when certain molecules, called allergens, that do not belong to our organism come into contact with the molecules produced by our immunitary system and called immunoglobulins. Specifically, the immunoglobulins responsible for allergic reaction are called Ige.

The Ige have a Y-shape and are produced by a particular category of lymphocytes. The terminal portions of short segments of this Y are different. This diversity is the basis of the specificity of each Ige. In fact, a specific Ige is able to bind to a specific allergen.
The long segment of Ige binds instead to the surface of the mast-cells. These are essentially balloons that produce and contain histamine. Once the Ige binds to the allergen, it triggers a reaction of disintegration of the mast-cells membrane, which release histamine into the surrounding tissues activating the allergic phenomenon.

As we've seen, if we come in contact with the tropomyosin of some vertebrates, molluscs, insects or nematodes, that can trigger allergic reactions. These allergies are usually specific and can be identified through specific tests.
Tropomyosins of some species including molluscs, crustaceans and some insects are so similar that a known sensitivity to one of these species almost certainly imply an allergy to the others.
Tropomyosin can trigger the allergic reaction also if inhalated, as already seen in the case of dust mites, and it's not denatured by cooking processes.